Process and apparatus for destroying hexavalent chromium in solution

ABSTRACT

An apparatus and method for precipitating and/or destroying a chemical material comprising a source of material connected in series with an acidification unit, a reduction unit, and a pH adjustment unit and with detention chambers between each unit and a container to allow settling of the newly formed material. This apparatus provides a circuit through which the reaction takes place within engineered volumes of piping surrounding the unit.

United States Patent 1191 Robertson 1451 Feb. 13, 1973 1 1 PROCESS ANDAPPARATUS FOR DESTROYING HEXAVALENT CHROMIUM IN SOLUTION [75] Inventor:Richard G. Robertson, Parma Heights, Ohio [73] Assignee: AyteksInternational Corporation,

Midina, Ohio [22] Filed: Jan. 11, 1 971 21 App1.No.i 105,163

[52] US. Cl. ..210/50, 210/60, 210/61,

210/96, 210/195, 210/256 51 Int. Cl ..C02c 5/02 [58] Field of Search..210/50, 62, 42, 60, 63, 96, 210/195, 256, 513, 61

[56] References Cited UNITED STATES PATENTS 3,005,554 10/1961 Kuntz..210/96 3,459,303 8/1969 Bradley ..210/96 OTHER PUBLICATIONS Sweglar,C., Plating Solutions, ldustrial Wastes, May 1959, PP. 4042 Pinkerton,H. L., Waste Disposal, Chapt. 11 of Electroplating Engineering Handbook,pp. 285-287, 290, 294 and 301-305 relied on Vohmann et al. ..210/54Primary ExaminerMichael Rogers AttorneyCharles L. Lovercheck, Esq.

[ 5 7] ABSTRACT An apparatus and method for precipitating and/ordestroying a chemical material comprising a source of material connectedin series with an acidification unit, a reduction unit, and a pHadjustment unit and with detention chambers between each unit and acontainer to allow settling of the newly formed material. This apparatusprovides a circuit through which the reaction takes place withinengineered volumes of piping surrounding the unit.

14 Claims, 9 Drawing Figures PROCESS AND APPARATUS FOR DESTROYINGHEXAVALENT CHROMIUM IN SOLUTION GENERAL DESCRIPTION OF THE INVENTION Theapparatus disclosed herein operates on the principle of acidification,reduction and then pH adjustment to allow settling of the newly formedmaterial. The chemical reactions take, place within engineered volumesof piping surrounding the module. The final settling of sludge takesplace within the main holding vessel.

OBJECTS OF THE INVENTION It is an object of the invention to provide adestruction unit which is continuous and automatic in operation.

Another object of the invention is to provide a continuous chemicalreaction unit.

GENERAL DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of themachine according to the invention.

FIG. 2 is a front view of the machine.

FIG. 3 is a right side view of the machine.

4 FIG. 4 is a left side view of the machine.

FIG. 5 is a top view of the machine.

FIG. 6 is a back view'of the machine.

FIG. 7 is a schematic view of the apparatus.

FIG. 8 is a schematic view of the tank.

FIG. 9 is a schematic view of the proportioning pump circuit.

DETAILED DESCRIPTION OF THE DRAWINGS The circuit shown in FIG. 7 is madeup of the three detention chambers 17, 25 and 32, which are connected inseries with the sight-glasses I4, 18, 26 and 33. These are, in turn,connected in series with the sump 11 and the holding tank 38.

A pump 13 circulates liquid from the sump 11 through the line 12 andthrough the system.

Acid isadded by means of a proportional acid injec tion pump 41 throughline 16 and check valve V to the acid injection point in line 12. Thedetection chamber 17 is sufflciently large in cross section and isinternally baffled in such a manner to provide approximately one minuteof turbulent detention in a typical example.

A pH cell 19 senses the pH of the liquid after it passes throughsight-glass l8 and controls a valve 2O so that when the pH is above apredetermined value, the liquid is recirculated through line 21 back tothe sump 11. If the pH is at or below the proper value, it proceeds intoline 22. pH cell 19 passes an electrical signal to proportionalcontroller 44 which, in turn, transmits a signal to proportional acidinjection pump 41. The controller 44 will balance the pump 41 outputrate such that said rate will stabilize at the desired setpoint toobtain correct pH at pH sensing cell 19. The liquid thence passesthrough line 22 to the reducing agent addition point 23 where a reducingagent injection pump 42 feeds reducing agent through check valve V andvalve 24 and line 24'. The liquid then continues through the detentionchamber 25 where it is held and mixed for a period of five minutes in atypical installation, thence through sight-glass 26 to the oxidationreduction potential detector 27. If the ORP reading is above or belowthe proper oxidation reduction potential range, the fluid is divertedthrough valve 28 into line 21 which recycles to sump II. If theoxidation reduction potential falls within the acceptable range, thefluid will continue into line 29. ORP cell 27 passes an electricalsignal to proportional controller 45 which, in turn, transmits a signalto reducing agent injection proportional pump 42. The controller 45 willbalance the pump 42 output rate such that said rate will stabilize atthe desired setpoint to obtain correct ORP at sensing cell 27. Theliquid thence passes through line 29 to the caustic addition point 30where caustic is added by way of a proportional caustic injectiorr pump43 through check valve V and through line 31 and valve 31'. The liquidthen continues through the detention unit 32 where it is held and mixedfor a period of one minute in a typical installation, thence throughsight-glass 33 and pH sensor 34 and into detention tank 38 primarychamber 35. If the pH is below a predetermined level, the liquid isrecirculated through pump 36 and line 37 to a point of injection in line29 prior to caustic injection point 30. If the liquid is within thedesired limits of pH, the liquid passes undisturbed from primary chamber35 into sump 38. pH cell 34 passes an electrical signal to proportionalcontroller 46 which, in turn, transmits a signal to proportional causticinjection pump 43. The controller 46 will balance the pump 43 outputrate such that said rate will stabilize at the desired setpoint toobtain correct pH at pH sensing cell 34. The newly formed solids in thefluid are allowed to settle, for example, for 2 hours thence clear wateris discharged through a pH cell and recorder 39 which will indicate thepH of the water discharged from the unit.

EXAMPLE A typical example of operation will be hexavalent chrome of1,200 ppm Cr at tank 11 which will be pumped by pump 13 at a rate of 5gallons per minute through sight-glass 14, chrome liquid will be yellowin color, and will have 60 cc. per minute of 66 Be- Sulfuric Acidinjected at 15 and it will be detained for a period of one minute at 17where its color will become a reddish-orange, which may be observed atsight-glass 18. If the pH is below 2.5 at pH cell 19, the liquid willproceed past point 23 where 12.6 pounds per hour of 98 percent puritysodium bisulfite will be injected and shall be detained and mixed for aperiod of five minutes at 25 thus changing the color of the fluid toemerald green which can be observed at sight-glass 26. If the oxidationreduction potential at ORP cell 27 is less than 2l0 mv and greater thanmv, the liquid shall then proceed past point 30 where 6.8 pounds perhour of 98 percent sodium hydroxide will be injected and shall bedetained and mixed for a period of one minute at 32 thus changing thecolor of the fluid to powder blue which can be observed at sight-glass33. If the pH of the liquid at pH cell 34 is greater than 8.0, it shallpass into tank 38 where it shall be held for two hours to allow thechrome hydroxide to settle and allow the clear supernate to pass throughpH recorder 39. Periodic removal of settled sludge will be accomplishedthrough blowdown port 40.

Typical chemical reactions that will occur within the above circuitryare as follows:

CIRCUIT l: v a third detention chamber and a second pH sensing umt,2Na2Cr04+ zHzsOt: H2cr2o7+ H2O+2Na2so4 said second pH sensing unithaving means thereon 2 2H2CrO4+2Na2SO4 for selectively directingmaterial from said third CIRCUIT 2; 5 detention chamber to said settlingchamber and to recirculate said material to said caustic unit if the pHis below a predetermined level, said second pH sensing unit beingconnected to a CIRCUIT 3; third proportional controller'w'herebyregulation is I achieved to inject exactly'the correct amount of al- '203 6N80H )s l' 2 4 kaline material to obtain desired pH.

The embodiments ofthe invention in which an exclu- The apparatus rcltedm clalm 3 "Y a first sive property or privilege is claimed are definedas folslght'glas s a Second gi -glass, a th rd sight-glass, and lows: 1a fourth sight-glass are disposed in said circuit, said first Anapparatus for destroying hexavalem chrome sight-glass being disposedprior to said acid injection comprising,

a series circuit including a first circuit element, Second slght'glassbemg dlsposed followmg 531d a chrome Source first detention chamber,

a first pump said third sight-glass being disposed in circuit adan acidinjection means, jacent said second detention chamber,

afirst detention and chemical reaction chamber, and Said fourthsightglass being disposed adjacent a PH Sensor means said thirddetention chamber.

a pH correction means, 6. The apparatus recited in claim 3 wherein areducameans ofdiverting unacceptable material, ing agent injection meansis connected in series with and a second detention chamber connected inSeries said circuit between said acidaddition unit and said with saidfirst detention chamber, third Circuit element,

said pH sensor being connected to control means on and F retenflon chamber and a diversion valve actuated by Said pH Sensor oxldation reductionpotential umt 1s connected to whereby Said material is recirculated tosaid 0 said circuit and means connected to said oxidation chrome Sourcewhen the pH of said material is reduction potential unit whereby saidmaterial will above a predetermined value, be diverted when theoxidation reduction potential said pH sensor being connected to aproportional atapredetermmed valuecontroller whereby exactly the amountof acid PP rlemoving a chemical ingredient required is injected toachieve desired pH. from a Solutlo" Compnsmg,

2. The apparatus recited in claim 1 wherein a reduca Source of SaidSolution ing agent additive unit is connected in series with said aSettling tank, first detention unit, a means of detecting oxidation, aplurality Oflarge Pipes and a plurality of Small P p reductionpotential, and a means of correcting amount 40 connected in Series witheach other and disposed of reducing agent additive by means ofaproportionate around Said tank, controller in order to achieve exactlythe correct Said Pipes each being disposed generally in the form amountof reduction agent, Ofa hBllX around Said tank,

and said second detention unit is connected in series means for addingmaterials to Said Solution Withinwith said reducing agent additive unitand said Said "8 P p sensing and controlling means. each said large pipehaving a diameter and length 3. The apparatus recited in claim 1 whereina third sufficient p i e a predetermined detention series of circuitelements is connected in series with t m u ing which said solution is inthe particular said mentioned elements, said large pipe,

said third circuit elements comprising a caustic addisaid large pipeshaving sufficient volume to provide tive unit, 7 said detention time ofa predetermined interval for a third detention chamber and a second pHsensing Said liquid flowing in Said Circuit,

unit, said material being adapted to precipitate solid said second pHsensing unit having means thereon material whereby said solids willsettle in said tank. for selectively directing material from said third8. A hro at destr ction module comprising a raw detention chamber tosaid settling chamber and to Waste Source, recirculate said material tosaid caustic unit if the 3 treated Waste p, pH is below a predeterminedlevel, a circuit connecting said treated waste sump to said said secondpH sensing unit being connected to a raw waste source,

third proportional controller whereby regulation is said circuitcomprising a first detention means and a achieved to inject exactly thecorrect amount of a]- second detention means, and a third detentionkaline material to obtain desired pH. means, 4. The apparatus recited inclaim 2 wherein a third means connecting said detention means in serieswith series of circuit elements is connected in series with each other,said mentioned elements, and said means connecting said detention meansin said third circuit elements comprising acaustic addiseries comprisinga first pH sensing device for tive unit, selectively recirculating saidliquid to said raw waste source when said pH is above a predeterminedvalue and connecting said circuit to said second detention means whensaid pH is below a predetermined value and continuously adjusting volumeof pH adjusting additive such that proper pH is obtained,

said circuit further comprises means to inject caustic into said circuitbetween said second detention means and said third detention means andmeans for recirculating said liquid from said circuit between said thirddetention means and said second detention means when the pH of saidliquid at said treated waste sump has a pH below a predetermined valueand transferring said liquid from said circuit between said thirddetention means and said treated waste sump when the pH of said liquidhas a pH above a predetermined value.

9. The circuit recited in claim 8 wherein said circuit comprises asecond detention means between said first detention means and said thirddetention means,

, and means to inject a reducing agent into said circuit at the end ofsaid first detention means adjacent said second detention means.

10. The circuit recited in claim 9 wherein means is provided torecirculate said material from said second detention means to saidchrome source when the ORP thereof is outside of a predetermined rangeand a means of continuously adjusting the volume of ORPadjustiveadditive such that stabilized proper oxidation reductionpotential is obtained and a means of circulating said material from saidsecond detention means to said third detention means when the oxidationreduction potential thereof is within a predetermined range.

1 1. The circuit recited in claim 8 wherein said circuit comprisesenlarged size pipes connected by reduced size pipes,

and said enlarged size pipes comprise a retention chamber.

12. The circuit recited in claim 1 1 wherein said pipes are connected toa tank and said pipes are arranged generally in the form of a helixaround said tank.

13. A process of destroying hexavalent chromium in solution comprisingcirculating said solution from a source through a series of lines anddetention chambers,

and adding acid and caustic to said solution in predetermined amounts tosaid solution comprising,

sensing said solution in said lines at a point subsequent to a firstdetention chamber and recirculating said solution when the pH variesabove a predetermined value,

passing said solution to an electrical signal means to proportionallycontrol an acid injection pump controlling the acidity of said solution,

passing said solution through a reducing agent addition point and addinga reducing agent to said solution,

passing said solution through a detention chamber to a pH detector andrecirculating said solution when the pH thereof downstream of the pointwhere said caustic is added is below a predetermined amount and allowingsaid liquid to pass through said line when the pH thereof is betweenpredetermined 14 'l" l method recited in claim 13 wherein said liquid ispassed from said caustic addition unit through an electrical signal to aproportional controller which transmits the signal to said causticinjection means whereby the rate of addition of caustic to said solutionis controlled.

1. An apparatus for destroying hexavalent chrome comprising, a seriescircuit including a first circuit element, a chrome source, a firstpump, an acid injection means, a first detention and chemical reactionchamber, a pH sensor means, a pH correction means, a means of divertingunacceptable material, and a second detention chamber connected inseries with said first detention chamber, said pH sensor being connectedto control means on a diversion valve actuated by said pH sensor wherebysaid material is recirculated to said chrome source when the pH of saidmaterial is above a predetermined value, said pH sensor being connectedto a proportional controller whereby exactly the amount of acid requiredis injected to achieve desired pH.
 2. The apparatus recited in claim 1wherein a reducing agent additive unit is connected in series with saidfirst detention unit, a means of detecting oxidation, reductionpotential, and a means of correcting amount of reducing agent additiveby means of a proportionate controller in order to achieve exactly thecorrect amount of reduction agent, and said second detention unit isconnected in series with said reducing agent additive unit and saidsensing and controlling means.
 3. The apparatus recited in claim 1wherein a third series of circuit elements is connected in series withsaid mentioned elements, said third circuit elements comprising acaustic additive unit, a third detention chamber and a second pH sensingunit, said second pH sensing unit having means thereon for selectivelydirecting material from said third detention chamber to said settlingchamber and to recirculate said material to said caustic unit if the pHis below a predetermined level, said second pH sensing unit beingconnected to a third proportional controller whereby regulation isachieved to inject exactly the correct amount of alkaline material toobtain desired pH.
 4. The apparatus recited in claim 2 wherein a thirdseries of circuit elements is connected in series with said mentionedelements, said third circuit elements comprising a caustic additiveunit, a third detention chamber and a second pH sensing unit, saidsecond pH sensing unit having means thereon for selectively directingmaterial from said third detention chamber to said settling chamber andto recirculate said material to said caustic unit if the pH is below apredetermined level, said second pH sensing unit being connected to athird proportional controller whereby regulation is achieved to injectexactly the correct amount of alkaline material to obtain desired pH. 5.The apparatus recited in claim 3 wherein a first sight-glass, a secondsight-glass, a third sight-glass, and a fourth sight-glass are disposedin said circuit, said first sight-glass being disposed prior to saidacid injection point, said second sight-glass being disposed followingsaid first detention chamber, said third sight-glass being disposed incircuit adjacent said second detention chamber, and said fourthsight-glass being disposed adjacent said third detention chamber.
 6. Theapparatus recited in claim 3 wherein a reducing agent injection means isconnected in series with said circuit between said acid addition unitand said third circuit element, and a second retention chamber isprovided and an oxidation reduction potential unit is connected to saidcircuit and means connected to said oxidation reduction potential unitwhereby said material will be diverted when the oxidation reductionpotential is at a predetermined value.
 7. An apparatus for removing achemical ingredient from a solution comprising, a source of saidsolution, a settling tank, a plurality of large pipes and a plurality ofsmall pipes connected in series with each other and disposed around saidtank, said pipes each being disposed generally in the form of a helixaround said tank, means for adding materials to said solution withinsaid large pipes, each said large pipe having a diameter and lengthsufficient to provide a predetermined detention time during which saidsolution is in the particular said large pipe, said large pipes havingsufficient volume to provide said detention time of a predeterminedinterval for said liquid flowing in said circuit, said material beingadapted to precipitate solid material whereby said solids will settle insaid tank.
 8. A chromate destruction module comprising a raw wastesource, a treated waste sump, a circuit connecting said treated wastesump to said raw waste source, said circuit comprising a first detentionmeans and a second detention means, and a third detention means, meansconnecting said detention means in series with each other, and saidmeans connecting said detention means in series comprising a first pHsensing device for selectively recirculating said liquid to said rawwaste source when said pH is above a predetermined value and connectingsaid circuit to said second detention means when said pH is below apredetermined value and continuously adjusting volume of pH adjustingadditive such that proper pH is obtained, said circuit further comprisesmeans to inject caustic into said circuit between said second detentionmeans and said third detention means and means for recirculating saidliquid from said circuit between said third detention means and saidsecond detention means when the pH of said liquid at said treated wastesump has a pH below a predetermined value and transferring said liquidfrom said circuit between said third detention means and said treatedwaste sump when the pH of said liquid has a pH above a predeterminedvalue.
 9. The circuit recited in claim 8 wherein said circuit comprisesa second detention means between said first detention means and saidthird detention means, and means to inject a reducing agent into saidcircuit at the end of said first detention means adjacent said seconddetention means.
 10. The circuit recited in claim 9 wherein means isprovided to recirculate said material from said second detention meansto said chrome source when the ORP thereof is outside of a predeterminedrange and a means of continuously adjusting the volume of ORP adjustiveadditive such that stabilized proper oxidation reduction potential isobtained and a means of circulating said material from said seconddetention means to said third detention means when the oxidationreduction potential thereof is within a predetermined range.
 11. Thecircuit recited in claim 8 wherein said circuit comprises enlarged sizepipes connected by reduced size pipes, and said enlarged size pipescomprise a retention chamber.
 12. The circuit recited in claim 11wherein said pipes are connected to a tank and said pipes are arrangedgenerally in the form of a helix around said tank.
 13. A process ofdestroying hexavalent chromium in solution comprising circulating saidsolution from a source through a series of lines and detention chambers,and adding acid and caustic to said solution in predetermined amounts tosaid solution comprising, sensing said solution in said lines at a pointsubsequent to a first detention chamber and recirculating said solutionwhen the pH varies above a predetermined value, passing said solution toan electrical signal means to proportionally control an acid injectionpump controlling the acidity of said solution, passing said solutionthrough a reducing agent addition point and adding a reducing agent tosaid solution, passing said solution through a detention chamber to a pHdetector and recirculating said solution when the pH thereof downstreamof the point where said caustic is added is below a predetermined amountand allowing said liquid to pass through said line when the pH thereofis between predetermined limits.